The following disclosure is based on German Application No. 101 34 281.0, filed on Jul. 13, 2001, which is incorporated into this application by reference.
The invention relates to a balance having a weighing pan, a weighing sensor, a housing that encloses said weighing sensor, and an antenna for identifying an object being weighed that is equipped with a transponder.
Balances of this type are known, for instance, from German Utility Model DE 299 14 925 U1. In the device described in that document, the antenna is arranged in a vertical plane, laterally above the weighing pan. This arrangement, however, limits the maximum size of the object to be weighed, since the antenna acts as a lateral stop, so that large objects to be weighed cannot be pushed far enough onto the weighing pan. If the objects to be weighed are small, the lateral arrangement of the antenna has the effect that the objects tend to be placed near the antenna and thus off center on the weighing pan. This results in eccentric load errors if the balance is not perfectly adjusted for eccentric loading.
Thus, one object of the invention is to provide an antenna arrangement that is suitable for both small and large objects to be weighed.
This and other objects are attained by arranging the antenna in a horizontal plane in or below the weighing pan and by making the weighing pan of an electrically poorly conductive material. According to one formulation, the invention provides a balance that includes a weighing pan; a weigh sensor; a housing enclosing the weigh sensor; and an antenna identifying an object being weighed that is equipped with a transponder. The antenna is arranged in a horizontal plane in or below the weighing pan, and the weighing pan is made of an electrically poorly conductive material.
According to another formulation, the invention is directed to a weighing system that includes: a balance having a weigh sensor; a housing that houses the weigh sensor; and a weighing pan having no more than low electrical conductivity; and an object having a transponder. The balance additionally includes an antenna that has high electrical conductivity and communicates with the transponder. At least an upper surface of the weighing pan is interposed between the antenna and the object
Due to the horizontal antenna arrangement in or below the weighing pan, the size of the object to be weighed is not limited. Even if the objects being weighed are small, the operator of the balance will intuitively place the object in the center of the weighing pan. This antenna arrangement is made possible because the weighing pan is made of an electrically poorly conductive material. Conventional metallic weighing pans would excessively attenuate the antenna in this arrangement. On the other hand, a small residual conductivity of the weighing pan is preferred, since it prevents electrostatic charging of the weighing pan and the object being weighed.